C Program To Implement Circular Doubly Linked List

If there's any direct connection(two way - from head to tail & tail to head) exists between head and tail of a list, then that list is called circular linked list.

See Also:

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C Program To Perform Insertion, Deletion, Sorting In Doubly Linked List - (Simple)
C Program To Sort A Doubly Linked List (Descending Order)

C Program To Merge Two Linked Lists

C Program To Reverse Linked List
C Program To Implement Circular Singly Linked List
C Program To Implement Circular Doubly Linked List
C Program For Polynomial Multiplication Using Linked List 
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Insertion, Deletion, Traversal, Reversal And Search Operation on Arrays
Doubly Linked List - Insertion, Traversal, Searching, Delete Node, Delete List

Example Program for Circular Doubly Linked List Implementation(in C):

---

  #include<stdio.h>
  #include<stdlib.h>

  struct node {
        int data;
        struct node *prev, *next;
  };

  struct node *head = NULL, *tail = NULL;

  struct node *createNode(int);
  void insertNode(int);
  void deleteNode(int);
  void display();

  struct node* createNode(int data) {
        struct node *ptr = (struct node *)malloc(sizeof (struct node));
        ptr->data = data;
        ptr->prev = NULL;
        ptr->next = NULL;
        return (ptr);
  }


   /* insertion in circular linked list */
  void insertNode(int data) {
        struct node *temp, *ptr = createNode(data);
        /* list is empty */
        if (!head) {
                head = ptr;
                head->next = head;
                head->prev = head;
                tail = head;
                return;
        } else {
                /* only one node present in list */
                if (head->next == head && head->prev == head) {
                        temp = head;
                        ptr->next = temp;
                        ptr->prev = temp->prev;
                        temp->prev = ptr;
                        temp->next = ptr;
                        tail = ptr;
                } else {
                        /* do insertion next to head */
                        temp = head->next;
                        ptr->next = temp;
                        ptr->prev = temp->prev;
                        temp->prev->next = ptr;
                        temp->prev = ptr;
                }
        }
  }


  void deleteNode(int data) {
        struct node *ptr, *temp = head;
        /* if list is not present */
        if (head == NULL) {
                printf("Data unavailable\n");
                return;
        } else if (temp->data == data) {
                /* deleting head node */
                if (head == tail) {
                        temp->prev = NULL;
                        temp->next = NULL;
                        free(temp);
                        head = tail = NULL;
                } else {
                        temp->next->prev = tail;
                        tail->next = temp->next;
                        head = temp->next;
                        temp->next = temp->prev = NULL;
                        free(temp);
                }
        } else {
                while (temp->next != head && temp->data != data) {
                        ptr = temp;
                        temp = temp->next;
                }
                if (temp->next == head && temp->data != data) {
                        printf("Given data unvavailable in list\n");
                        return;
                } else if (temp->next != head && temp->data == data) {
                        /* deleting any node in between head & tail */
                        ptr->next = temp->next;
                        temp->next->prev = temp->prev;
                        temp->next = NULL;
                        temp->prev = NULL;
                        free(temp);
                        printf("Data deleted successfully\n");
                } else if (temp->next == head && temp->data == data) {
                        /* deleting the tail node */

                        ptr->next = temp->next;

                        temp->next->prev = ptr;

                        tail = ptr;

                        free(temp);

                        printf("Data deleted successfully\n");

                }

        }

  }

  /* traversing the list */

  void display() {

        struct node *ptr = head;

        int i = 0;

        while (ptr) {

                printf("%-3d\t", ptr->data);

                if (ptr->next == head)

                        break;

                ptr = ptr->next;

                i++;

        }

        printf("\n");

  }

  int main() {

        int ch, data;

        while (1) {

                printf("1.Insertion\t2.Deletion\n");

                printf("3.Display\t4.Exit\n");

                printf("Enter ur choice:");

                scanf("%d", &ch);

                switch (ch) {

                        case 1:

                                printf("Enter data to insert:");

                                scanf("%d", &data);

                                insertNode(data);

                                break;

                        case 2:

                                printf("Enter data to delete:");

                                scanf("%d", &data);

                                deleteNode(data);

                                break;

                        case 3:

                                display();

                                break;

                        case 4:

                                exit(0);

                        default:

                                printf("please enter right option\n");

                                break;

                }

        }

        return 0;

  }

  Output: (Insertion, Deletion, Traversal In Circular Doubly Linked List)

  jp@jp-VirtualBox:$ ./a.out
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:1
  Enter data to insert:10
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:1
  Enter data to insert:20
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:1
  Enter data to insert:30
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:3
  10 30 20
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:2
  Enter data to delete:20
  Data deleted successfully
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:3
  10 30
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:2
  Enter data to delete:10
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:3
  30
  1.Insertion 2.Deletion
  3.Display 4.Exit
  Enter ur choice:4